Shinchou Yuusha: Kono Yuusha ga Ore TUEEE Kuse ni Shinchou Sugiru

The goddess Rista summons a hero to help her hard mode video game-like world. The hero, Seiya, is exceptional in every way, but he is incredibly cautious to the point of buying three sets of armor (one to wear, a spare, and a spare for the spare) and going full power against weak slimes (just in case).